# Bone mass

The scale's estimate of the weight of mineral in your skeleton, a few kilograms in an adult, which is not a measurement of your bones.

Type: body_value · Unit: kg · Domain: Body Composition · Accuracy: Estimate · Importance: Context

Also called: bone mineral, bone weight

## In one sentence

The scale's estimate of the weight of mineral in your skeleton, a few kilograms in an adult, which is not a measurement of your bones.

## Why it matters, and why not here

Bone health matters a great deal later in life, but a bathroom scale cannot see it. The figure is produced from the same impedance reading as everything else, by assuming a typical proportion of mineral in lean tissue, and it changes mostly when your water does. The real measure is bone mineral density from a DEXA scan, a medical test your doctor orders and interprets, and the scale's "bone mass" has no relationship to it that you should act on.

## What moves it

Hydration and the scale's algorithm. Real bone mineral changes over years, not days.

## How Vitality Tracker uses it

Stored from the full scale reading and displayed; nothing scores on it, and VT never turns it into a density or a bone-health statement. If you have a DEXA bone density report, that lives with your lab results and is for your doctor to read.

## How far to trust the number

Estimate, and the least informative line on the scale screen. Leave it alone.

## Sources

1. Kyle UG, et al. Bioelectrical impedance analysis, part I: review of principles and methods. Clin Nutr 2004;23:1226–43. [doi:10.1016/j.clnu.2004.06.004](https://doi.org/10.1016/j.clnu.2004.06.004).

## Related

- [Fat mass and lean body mass](https://vitalitytracker.app/knowledge/fat-mass-and-lean-body-mass)
- [DEXA](https://vitalitytracker.app/knowledge/dexa)
- [Bioimpedance: the smart scale](https://vitalitytracker.app/knowledge/bioimpedance)

Reviewed October 2026 · v1

Source: https://vitalitytracker.app/knowledge/bone-mass